System and method of diagnosis through detection of mechanical waves in refrigeration systems and/or household appliances

ABSTRACT

The present invention relates to a system and a method of diagnosis for a refrigeration system and/or household appliance which, based on a multiplicity of physical magnitudes detected, determine and inform the operating condition of said refrigeration system and/or of its components. Basically, the magnitudes are divided into two groups, namely: (i) those from which spectral signatures will be generated (magnitudes relating to mechanical vibrations); and (ii) magnitudes from which spectral signatures will not be generated. The spectral signatures are compared with the standard signatures, and the diagnosis is provided Digital based on this comparison. After the operating condition has been diagnosed, it is stored in a database, and a processing record of the system operation is updated. The operating central conditions are made available for viewing, and based on the record viewed, it is possible to determine whether or not the refrigeration system and/or household appliance and the components thereof are malfunctioning or not. The application further describes a compressor whose diagnosis can be determined by the method and system of diagnosis according to the present invention.

This application claims priority of Brazilian patent case No.P10702369-3 filed on May 29, 2007, the disclosure thereof being herebyincorporated by reference.

The present invention relates to a system and a method of diagnosis thatenable the operating conditions of household appliances, refrigerationsystems and/or components thereof to be made available to be viewedimmediately or later. The present invention further relates to acompressor diagnosed by the system and method of diagnosis of thepresent invention.

DESCRIPTION OF THE PRIOR ART

Refrigeration systems, in general, are widely known by most people.Thus, since these systems are, in many cases, considered to be a humanneed, it is interesting to develop methods that are able to manipulate,control or diagnose their operation. However, before mentioning sometypes of methods for controlling refrigeration systems, a typicalprior-art example of a refrigeration system and of the applicationthereof should be described.

Typically, a refrigeration system comprises a circuit, wherein a coolingfluid travels through several components, during which travel the volumeof the fluid is expanded and compressed, and its temperature andpressure rise and fall. It is important to observe the closerelationship between the aforementioned magnitudes when dealing withfluids.

The components which form an ordinary refrigeration system are, forexample: compressor, evaporator, condenser and capillary tube. Thecompressor, as the name itself indicates, compresses the cooling fluid,increasing its pressure and consequently its temperature, so that thefluid is pumped and forced to flow through the cooling circuit.

After leaving the compressor, the cooling fluid circulates through thecondenser, which is responsible for decreasing the fluid temperaturewithout decreasing its pressure. This condenser is usually a long ductarranged in such a way as to have rectilinear parallel parts connectedto one another, at their ends, by sinuous or curved parts, substantiallyshaped like an “S”. Thus, because this condenser is in contact with theenvironment, the cooling fluid loses heat to the environment as itcirculates inside the condenser, thus having its temperature decreased.

From the condenser, the cooling fluid moves to the capillary tube, alsoknown as expansion valve, whose function is to create resistance to thepassage of the fluid, thus causing a large pressure difference betweenthe fluid in the condenser and the fluid in the next component: theevaporator, where the pressure is low. Thus, due to the differencebetween the low pressure in the evaporator and the high pressure andfluid resistance in the capillary tube, the cooling fluid undergoes anabrupt transition when it moves towards the evaporator, having itsvolume suddenly expanded and being inserted into a low pressureenvironment. Therefore, considering the close relationship between thetemperature, pressure and volume magnitudes, it can be concluded that:if the volume increases and the pressure decreases, and the temperatureof the cooling fluid also decreases, which contributes to the absorptionof the environment heat in contact with said evaporator.

Finally, the cooling fluid, in this condition of expanded volume, lowpressure and low temperature, moves from the evaporator to thecompressor, where its volume is then reduced and its pressure andtemperature are increased, restarting the refrigeration cycle.

The typical system exemplified above can be applied in householdrefrigerators, air conditioners, commercial refrigerators, productdisplay refrigerators and any other device that needs to be refrigeratedor to have refrigeration.

Now that a refrigeration system has been described, we get back to thequestion of how its operation can be controlled, diagnosed ormanipulated. In this regard, it should be pointed out that the prior artdoes anticipate a system and method to control the temperature inrefrigeration and heating systems, however, it does not provide a methodor system to diagnose malfunction and thus prevent major failures whichcan occur in this system.

Therefore, with respect to the diagnosis of a refrigeration system, itis fair to say that for said system to work properly, differentrobustness characteristics are required from the refrigeration systemand from its components (fan, thaw resistance, shutdown valve,compressor etc.). However, these characteristics may vary depending onthe environment where the refrigeration system is, considering that eachenvironment has specific characteristics, which can vary with time, suchas, for example: humidity, dust and ventilation. Moreover, other factorscan alter the robustness properties of the components, among which thecondition of use, wear and aging of the components. That is, along theiruseful life, the components, as any physical device, are subjected towear and alterations in their working capacity due to the conditions ofthe environment or of use.

Thus, the conditions of use, wear and aging of the components can causefailures in these devices, which will reflect on the efficacy of therefrigeration system. These failures can be classified into two groups:(i) full collapse; and (ii) slight deviation.

In the full collapse situation, the defective element of the system canexhibit irregular or intermittent operation or can be completelyinactive, jeopardizing the whole refrigeration cycle. Thus, a failure ofthis magnitude can bring huge losses, firstly because the elements of atypical refrigeration circuit are arranged in series, that is, onedefective device can paralyze the activities of the system.

Secondly, the losses resulting from this type of failure occur, in somecases, due to the slow process of identification of the malfunction,since the system has very large time constants and the user can onlynotice a deviation in the refrigeration cycle after a long time haspassed. In this scenario, when the defect is not detected, even if thesystem is still working, it will not operate correctly and will overloadthe components, substantially reducing their useful life. In many cases,the loss caused by the damage to the refrigerated load can exceed thecost of maintenance of the refrigeration system.

On the other hand, in the situation where there is a slight deviation inthe operation the process to identify the defective element is evenslower and more difficult, since the malfunction is easily mistaken forvariations that the system can present due to changes in the temperatureof the environment and/or in the thermal load. Thus, when a failure ofthis type is finally identified, the time during which the system wasmalfunctioning, unfortunately, may have been enough to jeopardize one ormore components or even the refrigerated load. In addition to thiscomplication, in most cases, the process for identifying the defect isperformed empirically and based on the previous experience of the personin charge of the maintenance.

Additionally, some refrigeration system failures are caused by improperhandling by the user and by the little attention given to theidentification of the use by the people around or even interacting withthe refrigeration system in an improper manner.

Nonetheless, when the concept of refrigeration system is extrapolatedfor the purpose of making diagnoses and household appliances in generalare considered, the same types of failures and difficulties regardingtheir identification occur.

In this context, up to this moment, the prior art has not disclosed anysystem or method of diagnosis that is able to detect failures incomponents of a refrigeration system or in household appliances ingeneral by using means that detect both magnitudes internal to therefrigeration system or household appliance and magnitudes representingcharacteristics of the environment or of the load to be refrigerated, inthe case of a refrigeration system, alerting the user to the need forpreventive maintenance, minimizing the downtime of the equipment.

Due to this gap in the prior art, there is nowadays no compressor, oranother rotating element, of a refrigeration system being diagnosed by asystem or method of diagnosis which is able to detect failures and whichuse means to detects magnitudes that are inside and outside thecompressor, alerting the user to the need for preventive maintenance.

OBJECTS OF THE INVENTION

Therefore, the first objective of the present invention is to provide amethod of diagnosis that is able to define the steps required to performthe diagnosis of the working condition of a refrigeration system or ahousehold appliance.

The second objective of the present invention is to provide a diagnosissystem for refrigeration systems or household appliances that is able todetect specific malfunctions relating to each component to be monitored.Finally, the third objective of the present invention is to provide arefrigeration system compressor whose diagnosis is defined by the systemand/or method of diagnosis cited in the previous paragraphs.

BRIEF DESCRIPTION OF THE INVENTION

The first objective of the present invention is achieved by means of amethod of diagnosis for refrigeration systems or household appliances,comprising the steps of:

(i) Detecting signals, wherein vibrating mechanical wave signals orsound pressure signals from the refrigeration system and the environmentnear the system or the appliance are detected;

(ii) Generating a spectral signature of the vibration parametersdetected in step (i);

(iii) Assessing the operating condition of the components of therefrigeration system or household appliance: wherein the spectralsignatures generated in step (ii) are compared with the spectralsignatures relating to normal operating conditions of the refrigerationsystem or household appliance;

(iv) Updating the records: the operating condition of the components ofthe refrigeration system or household appliance assessed in step (iii)is registered in a database; and

(v) Operating condition alert/signaling: wherein the operating conditionassessed in step (iii) is made available for viewing.

The second objective of this invention is achieved by means of adiagnosis system for a refrigeration system or household appliances ingeneral, comprising at least:

-   -   a transducer that is able to detect mechanical vibrations or        sound pressure waves of the components of the refrigeration        system as a whole and its surroundings or of the household        appliance and its surroundings; and    -   a digital processing unit that receives the parameters obtained        by the transducer and is able to identify spectral patterns from        the signals received from the transducer.

The diagnosis system determines the operating condition by comparing thespectral patterns identified with spectral patterns previously stored ina memory unit.

The third objective of the invention is achieved by means of arefrigeration system compressor whose diagnosis is made using the systemand/or method of diagnosis of the first and second aims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described below in more detail, based onan example of execution represented in the drawings. The figures show:

FIG. 1—a schematic view of the diagnosis system according to the presentinvention, including the preferred embodiment with the alternativeembodiment; and

FIG. 2—a flowchart of the method of diagnosis according to the presentinvention.

DETAILED DESCRIPTION OF DRAWINGS

Firstly, before starting the description of the system and of the methodthemselves, the various concepts and particularities involved in thesubject matter of the present invention should be described, dividedinto topics as follows.

The Refrigeration System and Household Appliance

The refrigeration system whose operating conditions are to be diagnosedby the method and system of the present invention can be used fordifferent refrigeration purposes, such as: commercial refrigerators,household refrigerators, freezers, air conditioners etc. The method andsystem of the present invention can also be used in possibilities otherthan the ones exemplified.

Preferably and conceptually, the refrigeration system to be diagnosed isdefined as a system comprising the basic refrigeration elements, namely:compressor, condenser, expansion device and evaporator, and whoseoperation occurs as provided in the prior art.

Moreover, the present invention also contemplates in its system andmethod of diagnosis the possibility of diagnosing the operatingconditions of a household appliance, not only of a refrigeration system.The household appliance may be any appliance known in the prior art thatcan be diagnosed by the method and/or system of diagnosis of the presentinvention.

Magnitudes and Transducers

For the system and method of diagnosis of the present invention tooperate, several magnitudes need to be measured.

Thus, among the several physical magnitudes involved in a refrigerationsystem or in a household appliance, the ones that will preferably beused in the system and method of the present invention can be dividedinto two groups, namely:

(i) Mechanical wave signals or sound pressure waves of the components ofthe refrigeration system or of the refrigeration system as a wholeand/or of the household appliance and of the surroundings of therefrigeration system and/or household appliance; and

(ii) parameters of the refrigeration system and of an environment to berefrigerated, or parameters of the household appliance.

As will be shown below, the first group is more important in determiningthe operating condition of the system, while the second group is used toreinforce or confirm the analysis made based on the first group.

More specifically, the magnitudes of group (i) are mechanical vibrationsof the components of the refrigeration system and/or of the householdappliance, which vibrations are caused by the fact that the componentsare associated with at least one compressor or another rotating elementwhich may integrate the refrigeration system. This group furthercomprises the noise generated by the movement of people in thesurroundings of the refrigeration system and/or of the householdappliance.

The magnitudes of group (ii) are preferably, though not limited to, thefollowing: external temperature; temperature of the environment to berefrigerated, in the case of the refrigeration system; voltage andelectric current of the components of the refrigeration system and/or ofthe household appliance.

Thus, in view of the need to measure the aforementioned magnitudes, aplurality of transducers is required to detect all these parameters, sothat, based on the data collected, the system and method of the presentinvention can diagnose the refrigeration system.

Therefore, at least one transducer 2, or a plurality of transducers 2,is responsible for detecting the magnitudes of group (i), that is, it isresponsible for detecting the mechanical wave signals, which can also bereferred to as mechanical vibrations or sound pressure waves of thecomponents of the refrigeration system, of the refrigeration system as awhole and/or of the household appliance, preferably comprising:accelerometers, microphones or audio sensors that are able to detect theaforementioned mechanical vibrations or sound pressure waves of thecomponents or, even, the noise generated by the people circulating orpresent in the surroundings of the refrigeration system and/or of thehousehold appliance. However, any combination of the cited preferredexamples can be used, that is, accelerometers, microphones or audiosensors can be used by themselves, or an accelerometer can be used withone or more microphones, or a microphone can be used with one or moreaudio sensors, and so on. Thus, it is obvious that the combination ofthese transducers is not a limiting factor to the scope of the presentinvention.

A second plurality of transducers 3, which is responsible for detectingthe magnitudes of group (ii), preferably comprises: at least onetemperature sensor to measure the internal temperature of therefrigeration system and, if applicable, of the household appliance; atleast one temperature sensor to measure the temperature external to therefrigeration system and/or to the household appliance; and voltage andelectric current sensors.

Preferably, the first plurality of transducers 2 comprises at least onemicrophone to detect the movement of people in the surroundings of therefrigeration system and/or of the household appliance and microphonesto detect the mechanical vibrations or pressure waves of therefrigeration system and/or household appliance.

These transducers 2,3, the first plurality and the second plurality, canbe placed in different positions of the refrigeration system and/or ofthe household appliance, depending on the magnitude to be detected. Inthis regard, for the first plurality of transducers 2, the microphone todetect the presence of people in the surroundings of the refrigerationsystem and/or household appliance, for example, should be put in a placewhere it can detect the noisy sound signals that indicate the presenceand the circulation of people nearby. Taking as an example arefrigeration system associated with a commercial refrigerator (commonlyused in supermarkets and also used to display products), the microphonein question can be placed in the front portion of the refrigerator,since this is the closest possible position to the people.

The external temperature sensors, in general, are preferably placed inthe external portion of the refrigeration system, whereas the internaltemperature sensor is placed in a position where it can detect thetemperature in the region of the load to be refrigerated, in the case ofa refrigeration system. Moreover, regarding the second plurality oftransducers 3, the voltage and electric current sensors should be placednear the components from which a complement or confirmation to thediagnosis can be generated, as will be explained below.

Spectral Signature

The system and method of diagnosis of the present invention uses thespectral signatures so that the operating condition of the refrigerationsystem can be determined and the user or the person in charge of themaintenance can be alerted.

The spectral signature can be defined as a translation of the behaviorof a component on the temporal basis into a magnitude in the frequencydomain, in other words, the spectral signature is equivalent to thefrequency spectrum of a vibrating element (motor, compressor, etc.). Inthe case of the present invention, the spectral signatures arepreferably generated by the first plurality of transducers 2, the oneintended to detect the mechanical vibration or the sound pressure wavesof the refrigeration system and/or of the household appliance, and alsoto detect the noise surroundings of the refrigeration system and/orhousehold appliance, that is, they are generated from mechanical wavesignals (vibration and sound). Thus, first the magnitudes in questionare detected by their respective transducers, and then, after theapplication of a specific algorithm, the frequency spectra, that is, thespectral signatures, are generated. Preferably, this specific algorithmis of the Fast Fourier Transform (FFT) type.

Thus, considering that a component of the refrigeration system, in anormal operating condition, vibrates in certain frequencies and hascertain amplitudes (both identified through its spectral signature),even the smallest variation in the operation will alter its usualfrequencies and amplitudes, and it will start to oscillate in other inother frequencies with other amplitudes, that is, in an abnormaloperating condition.

This can be observed if we take as an example a motor or even acompressor. In this situation, when the compressor vibrates in a normaloperating condition, it produces an audible noise at specificfrequencies and amplitudes, however, the sound of this noise is alteredwhen the motor is, for example, malfunctioning. In other words, if thesound consists of a series of frequencies and amplitudes relating tosaid frequencies, the altered sound of this malfunctioning motorindicates, automatically, a change in its normal operating condition,since the oscillation frequencies and the related amplitudes have beenaltered.

Based on this reasoning, an alteration in the operating condition can bedetected by comparing the spectral signature obtained in a normaloperating condition with the one generated from recently detectedvibrations. Thus, the operating condition of the system and/or householdappliance as a whole or of the components thereof associated with thefirst plurality of transducers 2 is duly monitored.

Similarly, in the case of detection of people in the surroundings of therefrigeration system and/or of the household appliance, the noisedetected is transformed into the frequency domain, so that a pattern offrequencies of noises relating to the amount of people is generated, andwhen this pattern is altered, a clear reading of a change in behaviorcan be obtained by comparing the spectral signature of the standardcondition with the one recently generated from the mechanical vibrationsof the sound detected.

Operation Patterns

For the diagnosis of the system to be confirmed, as aforementioned, thestandard spectral signature of the system needs to be compared with thespectral signature generated from the current operating conditions. Forthis purpose, the method and system of the present invention relies onstandard spectral signatures stored in a database. It should be furtherpointed out that the system and method of the present invention can usespectral signature ranges or intervals associated to an operatingcondition to make diagnoses. In this case, the comparison would be madebetween the signature generated and the range of signatures stored inthe database. Moreover, there is the possibility that the aforementioneddatabase has a series of standard values for the parameters that willnot generate spectral signatures, namely: current, voltage andtemperature, that is, non-vibrating signals. Thus, a comparison between,for example, a standard voltage and a read voltage can be made tocomplement or confirm the result of the diagnosis already obtained bycomparing spectral signatures. The system and method of the presentinvention also contemplates the possibility of storing operationpatterns for more than one vibration mode. Conceptually, a vibrationmode is the level at which the system and/or its components vibrate,that is, a level at which the components are set to oscillate. Forexample, a compressor set to work at zero or 3600 rpm comprises twovibration modes, namely: 0 and 3600 rpm. On the other hand, a variablespeed compressor can comprise a variety of vibration modes, due to thevariability of its rotation.

Thus, the database stores spectral signatures and operating conditionpatterns corresponding to each vibration mode that the components or thesystem has, that is, each mode of operation generates a specificspectral signature for a given related operating condition.

In this case, the comparison will be made only between the signaturesdefined or related to the same vibration mode, that is, if the signaturegenerated was based in a reading of a vibration at 3600 rpm, it will becompared with the standard spectral signature of the operating conditionfor the same rotation.

Preferably, the components of the refrigeration system have at least twomodes of operation, and, if applicable, may have more than two, as isthe case with a variable speed compressor.

Record of Use

As the system and method of diagnosis detect the parameters andvibrations obtained through the first and second pluralities oftransducers, the data relating to these consecutive readings are storedin the aforementioned database. These data include the date and time ofthe reading, the component that is being checked and the respectiveoperating condition thereof, so that a record of use is created.

This record of use contains the data of each measurement, so that it ispossible to keep track of the operating condition of the system and/orhousehold appliance and of their components over time. Thus, in case therefrigeration system and/or household appliance is suffering amalfunction of the slight deviation type, said malfunction will beeasily detected, since the user or the person in charge of maintenancewill be constantly notified that the system is presenting slightvariations in its operating behavior, thus excluding the possibility ofmistaking a slight deviation for a minor variation in the operatingconditions due to changes in the environment.

This confusion is cleared, in fact, when the record of use is analyzed,since the behavior of the physical magnitudes of the refrigeratingsystem and/or household appliance tend to adapt to the variations in theenvironment (for example, to the temperature variations) and go backinto balance after a short period of time, whereas in the situation ofmalfunction of failure, they tend to remain at an operating conditionother than the normal one for a longer period of time.

Alert and Signaling

After the spectral signatures (and, if applicable, the other magnitudeswhich do not generate spectral signatures) have been compared, thesystem and method of the present invention need to be able to alert theuser or the person in charge of maintenance to possible failures. Thus,the system and method of the present invention have an alert interface 6which, as the name indicates, gives the user early warnings aboutdeviations from the normal operating conditions of the system.

Preferably, this alert interface 6 comprises at least one display and/orterminals for a portable reading device to be connected, thus making theoperating condition available for viewing.

Therefore, with the system and method of the present inventionperiodically diagnosing the operating conditions of the refrigerationsystem and/or household appliance and informing the user of theseconditions, damages to their respective components can easily beprevented.

Diagnosis System

Now that the components and some particularities of the diagnosis systemhave been described, the interaction between the elements that form saidsystem should also be described. Thus, as can be seen from FIG. 1, thediagnosis system 1 of the present invention comprises: a first pluralityof transducers 2, a second plurality of transducers 3, a digitalprocessing unit 4, at least one memory unit 5 and an alert interface 6.It should be pointed out that FIG. 1 illustrates the preferredembodiment of the diagnosis system of the present invention incombination with an alternative embodiment, considering that the secondplurality of transducers 3 is optional for the realization of thepresent invention.

As aforementioned, the first plurality of transducers 2 detects themagnitudes relating to the mechanical vibrations both inside and outsidethe refrigeration system, collecting parameters regarding the movementof people and the oscillations of the refrigeration system.

In an alternative embodiment of this diagnosis system, the secondplurality of transducers 3 detects the magnitudes that will support andcomplement the diagnostic conclusions reached based on the mechanicalvibrations.

The magnitudes detected by the first and second plurality of transducers2, 3 will be transmitted to the digital processing unit 4, which will beresponsible for transforming the information read into a parameter toobtain the diagnosis. The association between the transducers and saiddigital processing unit 4 can be made by means of wires and cables or,if the designers and people skilled in the art prefer, by wirelesstechnology, and it is important to point out that the data transmissionmeans is not a limiting factor to the scope of the present invention,and therefore other means, forms and methods can be applied.

A memory unit 5, which stores in this database the standard spectralsignatures and predefined parameter values of the refrigeration systemand/or household appliance, in addition to the record of use (record ofdata obtained from the first and second pluralities of sensors), isassociated with the digital processing unit 4. This memory unit 5 ispreferably of the non-volatile type, such as, for example: EPROM,EEPROM, FLASH, among others.

Thus, for the diagnosis of the refrigeration system to be made, thedigital processing unit 4 is set to generate the spectral signatures ofthe parameters obtained from the first plurality of transducers 2, thatis, to identify spectral parameters from the signals received from atleast one transducer, to compare the signatures generated with thestandard spectral signatures and enter the record of use in the memoryunit 5 database.

From the comparison between the recently generated spectral signaturesand those corresponding the normal operating conditions stored in thedatabase, it can be instantly detected whether the refrigeration systemhas failures of the full collapse type if, for example, a component iscompletely inactive.

On the other hand, in case a component of the refrigeration systemexhibits an intermittent operation behavior, when the record of use ismade available for viewing, it will indicate the malfunction, since theinconstancy of the activity of the system or of one or more componentsover time will have been identified. The same reasoning applies toslight deviations in the operating condition, as already discussed.

In an alternative embodiment, in addition to the diagnosis made bycomparing spectral signatures, the diagnosis system of the presentinvention contemplates the possibility that other magnitudes may aid inascertaining the operating condition, and said aid works ascomplementary information for confirmation purposes. For example, incase a component is found to be in a condition of complete inactivity,the current, the voltage, the temperature or other magnitudes which donot generate spectral signatures can be used to verify and confirmwhether the component is indeed in inactive. In fact, the magnitudesthat are read but do not generate spectral signatures are interpreted,or not, based on predetermined values stored in the memory unit 5.

It should be further noted that this digital processing unit 4 isassociated with the alert interface 6, so that the data relating to theoperating conditions of the refrigeration system will be made availablefor viewing through said interface 6 as soon as they have been obtained.

Method of Diagnosis

More specifically, the diagnosis system of the present inventionprovides the user with information regarding the refrigeration systemand/or household appliance by means of a method of diagnosis which,through its steps, discriminates the actions performed by the diagnosissystem.

Step (i)—Signal Detection

According to this method, a flowchart of which is illustrated in FIG. 2,the first step is signal detection, which comprises the detection ofmechanical wave signals, vibrating signals or sound pressure signalsfrom the refrigeration system and/or household appliance. In analternative embodiment, this step may comprise the detection ofnon-vibrating signals relating to parameters of the system and/orhousehold appliance.

Physically, said mechanical wave signals correspond to the mechanicalwaves which propagate through air or through the structure of therefrigeration system and/or household appliance, that is, they comprisesignals relating to the noise generated by the people in thesurroundings of the refrigeration system and signals relating to themechanical vibration of the system and its components. The non-vibratingsignals, in turn, correspond to parameters which do not relate tomechanical oscillations measured to obtain the diagnosis of therefrigeration system, such as temperature, voltage and electric current,referring to the system as a whole or to one or more of its components.

Relationship Between Step (i) and the Diagnosis System

The signal detection step is carried out by the first and secondpluralities of transducers 2, 3. The mechanical wave signals aredetected by the first plurality of transducers 2 and the non-vibratingsignals are detected by the second plurality of transducers 3. Rightafter the detection, these signals are transmitted, as aforementioned,to the digital processing unit 4.

Step (ii)—Spectral Signature Generation

After the data detection, the method of diagnosis according to thepresent invention comprises the step of generating a spectral signatureof the mechanical wave signals. In this step, similarly to what happensin the diagnosis system, the signals detected are transformed into thefrequency domain for their spectral signatures to be then generated.

Relationship Between Step (ii) and the Diagnosis System

The spectral signatures of the second step of this method are generatedin the digital processing unit 4 of the diagnosis system by an algorithmof the Fast Fourier Transform (FFT) type.

Step (iii)—Operating Condition Assessment

Once the spectral signatures of the mechanical wave signals detectedhave been obtained, the method makes an assessment of the operatingcondition of the components of the refrigeration system and/or householdappliances, that is, the spectral signatures generated in step (ii) arecompared with the standard spectral signatures relating to the normaloperating conditions of the refrigeration system and/or householdappliance. This information would be enough to determine whether or notthe system is operating normally. However, in order to increase thereliability of the diagnosis provided by the method of the presentinvention, this step (ii) further comprises an interpretation of thevalues presented by the non-vibrating signals. Thus, the conclusionsregarding the vibrating signals will be validated, reinforcing andensuring the reliability of the diagnosis provided.

Similarly to what happens in the diagnosis system, this interpretationcan be made based on predetermined values, through comparisons, or not.

In case the system has different vibration modes, the spectral signaturegenerated will be compared with the standard spectral signature relatingto the mode of vibration detected, thus ensuring that the diagnosis isobtained for the same vibration mode.

Relationship Between Step (iii) and the Diagnosis System

The assessment of the operating condition is made in the digitalprocessing unit 4 by comparing the spectral signatures generated withthe ones relating to normal operating conditions previously stored inthe unit memory 5 database. Moreover, the digital processing unit 4further verifies the cohesion of the parameters relating to thenon-vibrating signals, interpreting them based on predefined values oron previously established settings. Thus, the diagnosis generated by thespectral signatures is confirmed by the non-vibrating magnitudes.

Step (iv)—Record Update

Once the operating condition of the components, and consequently of thesystem as a whole and/or of the household appliance, has been identifiedand confirmed, the method moves on to step (iv), which comprisesupdating the record of use, that is, the operating condition of thecomponents of the refrigeration system assessed in step (iii) and thevalues of the non-vibrating signals obtained in step (i) are registeredin a database.

Thus, with the creation of the record of use, it is possible to keeptrack of the variation of the operating condition of the refrigerationsystem and/or household appliance over time. Therefore, if thefrequencies and amplitudes of a component remain altered for period oftime exceeding the time required for them to adapt to the variations inthe environment, it can be concluded or verified that there is a failurein the system.

Relationship Between Step (iv) and the Diagnosis System

The record generated in step (iv) by the digital processing unit 4 isstored in the memory unit 5 database.

Step (v)—Operating Condition Alert/Signaling:

Once the record has been updated, the user or person in charge ofmaintenance needs to be informed of the operating condition so that, incase any abnormality is occurring, the proper measures can be taken tosolve the problem. Thus, the operating condition obtained in step (iii)is made available for viewing.

Relationship Between Step (v) and the Diagnosis System

The operating condition alert and signaling procedure of the diagnosissystem is performed by the alert interface 6, which, as aforementioned,can be a display or terminals to which a portable reading device will beconnected.

Compressor

In addition to the system and method of diagnosis, the present inventionfurther relates to a compressor which acts as a component of arefrigeration system and whose diagnosis is determined by the system andmethod of diagnosis according to the present invention.

This compressor can be any conventional compressor in which the methodand system of diagnosis of the present invention can be implemented.

Having described an example of a preferred embodiment, it should beunderstood that the scope of the present invention encompasses otherpossible variations and is limited only by the content of the appendedclaims, including therein the possible equivalents.

1. A method of diagnosis for refrigeration systems or householdappliances, said method comprising the steps of: (i) Detectingmechanical wave signals of the refrigeration system and of theenvironment near the system or household appliance, the mechanical wavescomprising mechanical oscillations of the surroundings of therefrigeration system or household appliance; (ii) Generating a spectralsignature of the vibration parameters detected in step (i); (iii)Assessing the operating condition of the components of the refrigerationsystem or household appliance: wherein the spectral signatures generatedin step (ii) are compared with the spectral signatures relating tonormal operating conditions of the refrigeration system or householdappliance.
 2. A method of diagnosis according to claim 1, wherein theoperating condition of the components of the refrigeration system orhousehold appliance assessed in step (iii) is registered in a database.3. A method of diagnosis according to claim 1, wherein the operatingcondition obtained in step (iii) is made available for viewing throughan alert interface.
 4. A method of diagnosis according to claim 1,wherein the mechanical waves comprise mechanical oscillations ofcomponents of the system, of the refrigeration system as a whole, or ofthe household appliance.
 5. A method of diagnosis according to claim 1,wherein for the different vibration modes of the mechanical wave signalsof the refrigeration system or household appliance, the database storesa plurality of spectral signatures relating to the standard operatingconditions.
 6. A method of diagnosis according to claim 5, wherein, instep (iii), the spectral signature generated from a vibration mode iscompared with a plurality of spectral signatures of standard operatingconditions, said standard signatures relating to the same mode ofoscillation as the spectral signature generated.
 7. A diagnosis systemfor a refrigeration system or household appliances in general, saiddiagnosis system comprising at least one transducer (2) that is able todetect mechanical wave signals from the components of the refrigerationsystem as a whole and its surroundings or from the household applianceand its surroundings; and a digital processing unit (4) that receivesthe parameters obtained by the transducer (2) and is able to identifyspectral patterns from the signals received from the transducer.
 8. Adiagnosis system according to claim 7, wherein the digital processingunit (4) identifies the current operating condition of the system bycomparing the spectral pattern of the signals with preestablishedpatterns stored in a memory unit (5).
 9. A diagnosis system according toclaim 7, wherein the digital processing unit (4) stores a record of theoperating conditions of the system and identifies its patterns ofbehavior over time.
 10. A diagnosis system according to claim 7, whereinthe transducer (2) comprises accelerometers, microphones and audiosensors.
 11. A diagnosis system according to claim 7, wherein the alertinterface (6) comprises at least one display or terminals for theconnection of a reading device.
 12. A refrigeration system compressordiagnosed by a method comprising: (i) Detecting mechanical wave signalsof the refrigeration system and of the environment near the system orhousehold appliance, the mechanical waves comprising mechanicaloscillations of the surroundings of the refrigeration system orhousehold appliance; (ii) Generating a spectral signature of thevibration parameters detected in step (i); (iii) Assessing the operatingcondition of the components of the refrigeration system or householdappliance: wherein the spectral signatures generated in step (ii) arecompared with the spectral signatures relating to normal operatingconditions of the refrigeration system or household appliance.
 13. Arefrigeration system compressor diagnosed by a diagnosis systemcomprising: at least one transducer (2) that is able to detectmechanical wave signals from the components of the refrigeration systemas a whole and its surroundings or from the household appliance and itssurroundings; and a digital processing unit (4) that receives theparameters obtained by the transducer (2) and is able to identifyspectral patterns from the signals received from the transducer.